Gas fuelled torches are commonly used for metal work such as cutting torches and scarfing torches. Scarfing torches employ a stream of oxygen gas and are used in the steel manufacturing industry to remove surface defects and impurities. Cutting torches are generally recognized to be one of the most efficient methods of cutting metal. In industrial processes for cutting slab steel at a casting or rolling mill and the like, cutting torches are often operated continuously. Such torches are occasionally damaged or subjected to blow out. Because an industrial process of this type cannot be halted to replace or repair torch equipment, a standby torch is generally kept lit and operating around the clock so that it can be used if the primary torch fails. The repeated and continuous operation of a standby torch consumes large quantities of gas fuel and compressed oxygen.
In other metal cutting applications using gas fuelled torches, the torch is often used sporadically while material marking, placement or other arrangements of material or personnel are in process. Shutting off a gas fuelled torch for short periods of time between jobs is considered to be inefficient because flame settings must be re-established each time torches are turned on and re-lit. Consequently, the torch is conventionally left on continuously, and may consume significant quantities of fuel and compressed oxygen between active work performances.
It is therefore desirable to provide a gas flow control system for a gas fuelled torch so as to change the torch operation modes without interference with the established flame settings of the torch.